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P0141






P0141-O2 SENSOR 1/2 HEATER PERFORMANCE

For a complete wiring diagram, refer to the Wiring Information.





Theory of Operation

The Oxygen Sensors (O2 Sensor) are used for fuel control and catalyst monitoring. Each O2 Sensor measures the oxygen content of the exhaust stream. When the engine is started, the Powertrain Control Module (PCM) operates in an Open Loop mode, ignoring the O2 Sensor signal voltage while calculating the air-to-fuel ratio. The heating elements inside each O2 Sensor heats the sensor to bring it to operating conditions faster. This allows the system to enter Closed Loop earlier and the PCM to calculate the air-to-fuel ratio sooner. While the engine runs, the O2 Sensor heats up and begins to generate a voltage within a range of 0-1,275 mV. Once sufficient O2 Sensor voltage fluctuation is observed by the PCM, Closed Loop is entered. The PCM uses the O2 Sensor voltage to determine the air-to-fuel ratio. An O2 Sensor voltage that increases toward 1,000 mV indicates a rich fuel mixture. An O2 Sensor voltage that decreases toward 0 mV indicates a lean fuel mixture. The Powertrain Control Module (PCM) makes short term and long term fuel corrections to maintain stoichiometric fuel/air ratio for best catalytic converter efficiency. Short term fuel correction is based on upstream O2 Sensor output and is designed for quick engine response. The long term fuel correction compensated for variations in the engine specifications, sensor tolerances and component aging and is designed to correct rich and lean conditions over a longer period of time.

- When Monitored:
Continuously during O2 Sensor Heater operation with battery voltage below 16.5 volts and no O2 Sensor circuit DTCs present.

- Set Condition:
The Powertrain Control Module (PCM) detects that the O2 Sensor Heater element resistance is above 4640 Ohms for 4 tests during this ignition cycle. The PCM cannot directly measure the heater resistance, therefore the heater rationality is determined as follows: A 1mA current is pulsed through the O2 Sensor circuit and the voltage across the sensor is measured. The heater health is inferred by this measurement. To avoid overheating and damaging the O2 Sensor, the resistance can only be measured periodically and during fuel cutoff. Two trip fault. Three good trips to turn off the MIL.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

Diagnostic Test

1. O2 SENSOR HEATER ELEMENT
1. Turn the ignition off.

NOTE: Allow the O2 Sensor to cool down to room temperature.

2. Disconnect the O2 Sensor 1/2 harness connector.
3. Measure the resistance of the O2 Sensor Heater Element across the O2 Sensor connector (component side) between the (K299) O2 Sensor Heater Control terminal and the (F344) Fused ASD Relay Output terminal.

NOTE: The O2 Sensor Heater Element resistance values should be measured at 21.1°C (70°F). The resistance value will vary with different temperature values.

Is the resistance of the O2 Sensor Heater Element between 2.0 and 30.0 Ohms?

Yes

- Go To 2

No

- Verify that there is good pin to terminal contact in the O2 Sensor 1/2 and Powertrain Control Module connectors. If OK, replace the O2 Sensor. .
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

2. ACTIVE DTC
1. Turn the ignition off.
2. Reconnect the O2 Sensor 1/2 harness connector.

NOTE: Wait a minimum of eight minutes to allow the O2 Sensor to cool down before continuing the test.

3. Start the engine and allow it to run for at least five minutes.
4. With the scan tool, view DTCs.

Is the DTC active at this time?

Yes

- Go To 3

No

- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test.

3. (K299) O2 SENSOR 1/2 HEATER CONTROL CIRCUIT OPEN/HIGH RESISTANCE
1. Turn the ignition off.
2. Disconnect the O2 Sensor 1/2 harness connector.
3. Disconnect the PCM C1 harness connector.
4. Measure the resistance of the (K299) O2 Sensor 1/2 Heater Control circuit between the O2 Sensor 1/2 harness connector and the PCM C1 harness connector.

Is the resistance below 0.5 Ohms?

Yes

- Go To 4

No

- Repair the excessive resistance in the O2 1/2 Heater Control circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

4. (F344) FUSED ASD RELAY OUTPUT CIRCUIT OPEN
1. Remove the ASD Relay.
2. Measure the resistance of the (F344) Fused ASD Relay Output circuit between the ASD Relay Output terminal and the O2 Sensor 1/2 harness connector.

Is the resistance below 0.5 Ohms?

Yes

- Go To 5

No

- Repair the (F344) Fused ASD Relay Output circuit for an open circuit or short to ground.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

5. POWERTRAIN CONTROL MODULE (PCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Oxygen Sensor 1/2 and the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the O2 Sensor and Powertrain Control Module harness connectors.
4. Perform any Technical Service Bulletins that may apply.

Were there any problems found?

Yes

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Replace and program the Powertrain Control Module. .
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

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